The present invention relates to a production tube with an integrated hydraulic line.
When an oil well is put into production the standards of safety stipulate that the well head must be equipped with a subsurface safety valve arranged in the well at a depth of about 30 m under the surface (ground or sea bed). This valve is intended to close off the well in the case of an incident, and in the majority of installations is hydraulically actuated.
In a general way, the safety valve arranged at depth is designed to have a closed rest position, the valve being held in an open position under the effect of the hydraulic pressure sent from the surface. In the case of an incident, the hydraulic pressure is purged, which results in the closing of the valve. Thus, in the case of destruction of the well head, the safety valve closes automatically.
The hydraulic passage is constituted, in a conventional way, by a hydraulic conduit of small diameter --for example 6 mm--which is arranged outside the production tubes between the valve and the well head which is arranged either on the surface or at the bottom of the sea. However, the hydraulic line has to be put in place on the tubes before the installation of the latter into the well. This procedure has numerous disadvantages.
The presence of a hydraulic line on the outside of a tube which is lowered into a well means that the line is at risk of mechanical damage or even crushing as a result of more or less violent contacts between the tube and the casing, or even indeed on passing into the blowout preventer. The resultant hydraulic leak necessitates a costly loss of time especially for offshore wells in order to effect the replacement of the damaged conduit. Still more serious, this leak can come to light much later, then requiring intervention with an apparatus which is especially hired for the purpose. Moreover, the hydraulic conduit, arranged between the tubes and the casing, is in an environment which can be or can become corrosive, constituted, for example, by brine, by sulphate reducing bacteria, by traces of corrosive gas etc., an environment which can attack the hydraulic conduit in the more or less long term.
Another problem is found at the level of the safety closing devices which are configured to close off the well with the production tubes in the well. These closing devices are equipped with semi-circular jaws which interact in a leakproof way with the outer surface of the tube. The presence of the hydraulic conduit on this outer surface can give rise to leaks at the level of the jaws or deterioration of the latter.
It has already been proposed to overcome these drawbacks with an assembly formed by two tubes arranged concentrically, the hydraulic fluid passing through the annular space formed between the tubes. Apart from the volume of fluid necessitated by this configuration, this concept presents serious drawbacks, for example on the level of the leaktightness and of the coupling between the concentric elements.
Metal protectors or protectors in elastomer have also been proposed, which are mounted, at intervals, around tubes with the hydraulic line rigidly embedded and intended to protect the conduit from mechanical impacts. This type of device cannot resolve all the drawbacks set out above.